


,,..,, ~^APER TESTING MBl 

.C6 

Copy 1 Microscopical, A^ilCilU^Ul, I-IHU ? M) ■■v^'..ai ±-i 

Described, with an Account of the 
Apparatus Employed 



FREDERICK C. CLARK 

Cu.irman ot the Committee on Papsr Testing o{ ibi 
i..i:.iical Ahsooiatioi ot ehc Pirlp and Paper Indusfiy 



Nev/ Yoi-k " U. S., A 
T.\PP1 PU BUS HIT 

1920 



T.A.P.P.L PUBLICATIONS 



Modern Methods of 
Testing Paper 

A knowledge of recent advances in paper 
testing methods is essential to the mental 
equipment of paper technologists and, in- 
deed, for all who have anything to do with 
the manufacture or sale of paper. The 
Technical Association has just issued a 
work by Frederick C. Clark, Chairman of 
the T. A. P. P. I. Paper Testing Committee, 
bearing the title 

"PAPER TESTING METHODS" 

which constitutes a practical treatise on the 
microscopical, physical and chemical analy- 
sis of paper. Illustrations of testing devices 
and apparatus are given and methods are 
included for the identification of various 
kinds of loading materials used in paper 
making. Formulas for stains and chemical 
reagents used in the detection of fibers, and 
their application, are given in detail and 
there is a chapter on the fibers used or 
proposed for use in papermaking. Copies 
will be sent postage prepaid for $1.00. 

American Papermaking Woods 

Are you interested to know the native 
American woods that are suitable for paper 
pulp manufacture? A pamphlet telling all 
about the character and yields of pulp that 
may be expected from different woods can 
be obtained by ordering 

"AMERICAN WOODS FOR 
PULP AND PAPER" 

Price 25 cents postpaid. 



The Creative Workman 

Do you wish to know how the joy of work 
can be stimulated and industrial efficiency 
enhanced through creative workmanship — 
all with reference to the operations of a 
Pulp and Paper Mill? Then read 

"THE CREATIVE WORKMAN" 

By ROBERT B. WOLF 
Price 25 cents postpaid. 

Mill and Laboratory Practice 

Every mill superintendent, engineer or 
chemist should possess a copy of 

"TECHNICAL ASSOCIATION PAPERS, 
SERIES II." 

It is a cyclopedia of mill and laboratory 
theory and practice. In addition to a com- 
plete descriptive list of books and periodi- 
cals pertaining to pulp and paper manufac- 
ture, there are articles on 

Analytical Methods; 
American Papermaking Clays; 
Making Cellulose from Cotton Linters; 
History of the Sulphite Process; 
Soda Mill Problems; 
Tearing Tests for Paper; 
Testing Methods for Sulphite Acid; 
Discussions of Heat, Light and Power 

Problems; 
Handling of Woodroom Refuse; 
Principles of Accounting and Control of 

Industrial Power Plant Costs; 
Mill Lighting Systems; 
Sizing Up Men for Positions; 
Important Factors in Grinding Wood for 

Pulp, etc. 
Price $2.00 postpaid. 



Address all orders to The Secretary 
Technical Association of the Pulp and Paper Industry 
Eighteen East Forty-First Street - New York 



PAPER TESTING METHODS 

Microscopical, Chemical, and Physical Processes Described 
with an Account of the Apparatus Employed 

By FREDERICK G. CLARK 

Chairinau of the Coiiiinitlce on Paper Testing <.f the 
Technical Association of the I'uli) and Paper hulustry 



New York - U. S. A. 

TAPPl PUBLISHING CORPORATION 

1920 









"I- i) ^^'^ ^ 



.0 



,.^ 



& 



-:• I 



iT^lX 



PAPER TESTING METHODS 

Microscopical, Physical, and 
Chemical Processes Described 

By FREDERICK C. CLARK 
Chairman of the Committee on Paper Testing of the Technical Association of the Pulp and Paper Industry 




HE Paper Testing Committee of the 
Technical Association of the Pulp 
■md Paper Industry presents the fol- 
lowing revision of its previous work 
on Paper Testing, for the considera- 
iion of the association. This revision 
constitutes additions and corrections 
to the report of the Committee on 
Paper Testing as previously published. 
Recent advances in paj)er testing methods have de- 
veloped new procedures and shown the need of 
changes in some few of the previous methr)ds. 

All changes and additions to the previous report 
are presented to the association for cominent, and it 
must be understnod that sotne of them — for example : 
the qualitative tests for glue and rosin, can be only 
tentative until their application in general use has 
shown conclusively that they are worthy of adoption 
as standard methods. 

Under stains there has been added what is known 
as the "Jenk's stain" as a supj.ilement to the Herz- 
berger stain for papers containing small amounts of 
rag. 

Under testing devices, there have been included 
photographs of the Thwing paper scale, the new 
Perkins quadrant paper scale and the Thwing tearing 
tester. 

A note on the meaning <if "Substance Number" is 
also included by way of explanation. 

Methods for determining the machine direction of 
paper are included. 

Much discus>iiin has t;iken jilace in the past regard- 
ing the use of the Schopper folding machine. In 
order to clarify certain points, there have beeti added 
detaileil instructions for calibrating the machine, to- 
gether with photographs showing the apparatus used 
in the calibrating method recommended. 

The subject of "gloss" or "finish" has been taken 
up, and a method using the Ingersoll glarimeter is 
describetl in tletail, together with a photograph of the 
app.aratus. .\n article on the use of the Ingersoll 
glarimeter is in course of preparation, and will 
shortly be [iresented to the association through its 
official journal. 

Under the head of "Specks in paper," there have 
been included detailed methods for identifying many 
kinds of dirt particles. These notes will prove helpful 
to many having work of this kind to do. 

Untler the head of "Fillers" have been added 
methods for the identification of various kinds of 
loadinsr materials used in papermaking. 

In order to simplify rosin determinations, there has 
been included ,i photograph and description of an 



extraction appaiatus that will be found not only to 
save time, Ijut is also more handy to use and less 
ex])ensive than the usual So.xhlet apparatus. 

Recent work has been carried out for the purpose 
of determining the percent of starch in paper. The 
method included herein is reconmiended both because 
of its accuracy and its simplicity. Methods are also 
in process of completion to permit a differentiation 
between beater or pearl starch and tub sizing or 
treated and converted starches. 

THE METHODS OF TESTING PAPER 

The testing of paper is divided into three parts — 
namely: Microscopical, physical and chemical. 

Hy microscopical examination the kind or kinds of 
fibers entering into the composition of a paper ma\' 
be determined The e.xperienced observer is able to 
estimate the proijortion of the various fibers used and 
such estimates are well within the limits of variation 
m the process of manufacture. By the use of the 
microscope it is often possible to indicate the presence 
of rosin size. It is also possible to distinguish dif- 
ferent kinds of starches by the characteristic sizes 
.md markings of starch grains. Soine indication of 
I lie be.-iting process is also secured as a light brushing 
action of the beater roll tends to fray out the ends 
of the fibers, whereas severe beating, with sharp 
tackle, cuts the fibers into smaller [lieces without any 
tendency to fray out the ends. 

The microscope is also of great assistance in help- 
ing to identify specks and dirt spots. A knowledge 
of the material that composes a dirt spot or S[)ecks 
will often give the clue as to where such s[)ols origi- 
nate, and means may thereb)- be taken to eliminate 
the cause. 

Pliysical Tcstbiij — Under this he.iding are included 
such tests as are enumerated l)elow, as follows: 

.Area of the sample. 

U'eii-^ht of the sample. 

Burstini,' strength per unit area. 

Thickness. 

Bulk or thickness of a miniher of sheets. 

Folding endurance. 

Tensile strength. 

Elongation at rupture. 

.\lisorption. 

Opacity. 

Gloss or glare. 

Translucency. 

Degree of sizing. 

Retention of loading. 

Breaking length. 

Chemical Analysis — By chemical analysis it is pos- 
sible to make the followina; determinations: 



PAPER TESTING METHODS 



Percent of ash. 

Qualitative test to indicate kind of loading material used. 

Percent of paraffin. 

Sizing material used. 

Coating material used. 

Presence of acids, free chlorine, etc. 

(See ch.irt of Paper Testing.) 

MICROSCOPICAL e.\a:mination 
Esliiiiatioii of Fiber Conicnt — Secure a representa- 
tive sample by clipping a piece of about the area of 
a cent from the corners of several of the sheets to be 
tested. Place the samples in a dish, small beaker, 
or test tube, cover with a 0.5 percent caustic soda 
solution and bring to a boil to remove sizing or 
other binding material. The jKCces are next drained, 
washed several times in tap water, rolled into a small 
pill or ball between the thumb and first finger for 
about one minute, then placed in a test tube, about 
half filled with water and shaken vi.gorously, so as to 
defiber thoroughly the particles of paper. A small 
part of this defibered mass is removed from the test 
tube by the aid of a microscopic needle (Note No. i) 
thoroughly dried on absorbent paper (Note No. 2) 
that is free from lint, placed on a microscopic slide 
and covered with several drops of Herzberg's stain. 
(Note No. 3.) The fibers are carefully pulled apart, 
by the aid of microscopic needles, so that they will 
not lie too much in a bunch and are then covered 
with the cover glass. (Note No. 4.) The slide is 
now ready for an estimation by the aid of the micro- 
scope. (Note No. 5.) 

It is suggested that after the small sample of paper 
has been boiled with 0.5 percent caustic soda, that 
the sample be next washed with 0.5 percent hydro- 
chloric acid and finally with water. It is difficult to 
wash all the caustic from the fibers and an addition 
of hydrochloric acid seems advisable. 

Note No. i. — There arc two mtthods in use for removing 
a representative sample of fibers from the test tube. 

First method. Use a test tube of about 5^-inch diameter 
and about 6 inches long, keep the fibers diluted with water, 
so that they will mix readily when shaken vigorously. The 
fibers mix very easily if the test tube is about two-thirds 
full of water and fibers. The microscopic needle referred to 
is a pointed steel needle imbedded in a small v;ood or metal 
handle. Shake test tube, and then quickly incline it at a 
sharp angle. Insert the point of the microscopic needle and 
remove a small bundle of fibers for use in making up the 
microscopic slide. The foregoing method of procedure is 
best where the fibers are long, such as in a rag bond, ledger, 
or writing paper, also for long-fibcred wood papers made of 
new sulpliitc or sulphate pulps. For groundv.ood papers, or 
where the fibers are very short and contain a large quantity 
of fine broken particles such as cooked old paper stock, the 
use of the needle to secure a representative sample will re- 
sult in securing more long fibers than short fibers, with a 
result of inaccuracy. For papers containing much short fine 
fiber it is best to use the second method. 

Second method. This was suggested by Ernest Mahler, 
general superintendent, and C. G. Bright, chemist, of the 
Kimberly-Clark Company, and later described in detail by 
George K. Spence, chief chemist, and John M. Krauss, as- 
sistant chemist. New York and Pennsylvania Company, in 
Paper, vol. XX, no. 11, pa.gc 12, \h\y 23, 1917. In using this 
second mcdiod it is advisable to have the fibers slightly more 
dilute in the test tttbe than is the case in the first method, 
also the test tubes should be about three-quarters of an inch 
in diameter by about 8 inches long. In place of the micro- 
scope needle a lo-inch glass tube of about seven thirty- 
seconds of an inch in diameter is employed. This glass tube 
has one end rounded so as not to have sharp ed.ges and the 
other end is provided with a small rubber bulb. This serves 
as a dropper. Spence and Krauss describe the modus oper- 
andi as follows: "When ready to prepare the slides, the test 
tidie is well shaken, the dropper inserted, with as little delay 
as possible, two inches below the surface, two bubbles of air 
expelled and a little less than half an inch of the mixture 



drawn into the tube. This is transferred to slides, com- 
pletely emptying the dropping tube, which will make four 
drops. The slides are placed in an air bath to expel mois- 
ture, cooled, and each drop stained with Herzberg stain, just 
before it is to be examined. The excess stain is then re- 
moved — after the colors have developed to a maximum point, 
about three minutes required — by tilting the slide and the 
cover glass placed over the spot." After the cover glass is 
in place, it should be pressed down gently to expel excess 
stain and any excess stain removed by absorbing it with a 
piece of blotting or filter paper. (See also Notes 2, 3 
and 4.) 

Note No. 2 — The absorbent paper used should have a 
hard, smooth surface so that no lint will adhere to the 
sample of fibers. As soon as the sample is dry it may be 
removed to the microscope slide and is then ready for the 
drop of stain. A second method of drying the sample is to 
put it on the microscope slide and then touch it with the 
corner of a piece of folded filter paper of ordinary quality. 
For this purpose a cheap grade of filter paper may be cut 
into pieces about ij^ inches by 4 inches. This makes a 
handy size for use in drj'ing the sample and also in removing 
the excess stain from around the edges of the cover glass. 
Care must always be exercised to prevent the sample of 
fibers to be tested from becoming contaminated with fibers 
from the absorbent paper or filter paper. A third method of 
drying the sample of fibers is to place them on a microscope 
slide and evaporate the moisture in a current of heated air, 
in an oven or by some other suitable arrangement. 

Under Note No. 2 in regard to drying the small 
sample of the fibers on the tnicroscope slide, atten- 
tion is called to the fact that the sample must be dried 
so that the stain will not be diluted and yet must not 
be dried too hard because then it is difficult to sepa- 
rate the fibers and the staining does not take place 
uniformly. 

herzberg's stain 

Note No. 3 — The Hcrzberg stain is made according to the 
following formula: 

Solution A — 20 .grams zinc chloride. 

10 Cc. of water (preferably distilled). 

Solution B — 2.1 grams potassium iodide. 
0.1 gram iodine crystals. 
5 Cc. of water (preferably distilled). 

Dissolve solutions A and B separately, then mix and allow 
to stand several hours, or until all sediment has settled out. 
The clear liquid is next decanted and is ready to be used 
in staining the fibers. All iodine solutions must be kept in 
the dark, as otherwise they deteriorate rapidly. The Hcrz- 
berg stain is a selective stain, that is, it has selective stain- 
in.g properties. Grotmd or mechanical woodpulp, jute, flax 
tow, uncooked manila hemp and in fact most every vege- 
table fibrous material containing large quantities of ligno- 
ccllulose, is colored yellow or lemon yellow. The removal 
of their lignoccllulose content changes the staining effect 
from a yellow to a blue or wine-red color, though jute and 
a few other fibers remain unchanged in color. Thoroughly 
cooked and bleached soda and sulphite pulps, cooked and 
bleached straw pulp and esparto are colored blue or navy 
blue. Cotton and linen rags, thoroughly cooked and bleached 
manila hemp, and certain of the Japanese fibers are col- 
i->red a wine red. 

In connection with the Herzberg stain, the follow- 
ing alternative formula is suggested : 25 Cc. zinc 
chloride solution (saturated) : 5.25 Gin. potassium 
iodide; 0.25 Gtn. of iodine, and 12.5 Cm. water. 
Owing to the difficulty of obtaining zinc chloride of 
uniform moisture content, it has been found more 
satisfactory to use a satitrated zinc chloride solution. 
By mixing the ingredients as stated above, the proper 
stain can be obtained at once. 

jenk's stain 

The stain known as "Jenk's Stain" is of value 

when it is desired to a-^certain definitely small 

amounts of rag fiber with only a poor Herzberg 

stain available : to 50 Cc. of saturated magnesium 



P A r !■: R T I-. S T I N C. M E T H O D S 



Testing or Paper to Determine Quality 



5 AMPLE. 



-Nlt-fckOUS Wool. t'Mflt 



Manila oit Jure 



"irWilLtoTRt^N-j 



r'i.AoTCRorPARtS 

OR Pearl Hakd- 

EHING 
' rliA-.'Y 3PAR 

;« Barium 

li'Jl-PMATf-- 

; Talc 
:";at;nVv>iite 



AHiKAL Glue 
lApHCSivt Material. ,^^^^,_^ 

[ CHINA Clay 

riUJNGKA^'fWiAL ; -SLAWcruti; 

. SAilN VVH-.TR 



CHART OF PAPER TESTING SYSTE1[ OF THE TECHNICAL ASSOCIATION 



PAPER TESTING METHODS 



chloride solution add 2J/2 Cc. of iodine potassium 
iodide solution made up as follows : potassium iodide, 
Gm. 2; iodine, Gm. 1.15, and water, 20 Cc. Use 
exact quantities and keep solutions from the light; 
the stain is kept best in a small brown bottle with a 
pipette. Rag fiber is stained brown, straw is stained 
blue-violet, groundwood is stained yellow, and chem- 
ical wood either no color or deep red. 

The following suggestions are offered to those just 
beginning these tests. 

It is absolutely essential to have a satisfactory 
stain or else the results will be worthless. To test 
out a stain make up a mixture of about equal parts 
of bleached soda pulp, bleached sul[ihite pulp and rag 
filter paper. Prepare a microscope slide from this 
mixture and stain with the stain to be tested. If the 
stain is correct, then the soda pulp should sho\\' a 
dark blue color, due to the thicker and more opaque 
fiber walls, the sulphite pulp should show a light 
blue, due to the thin fiber walls and the rag fibers 
will show a red or wine-red color. If the blue color 
is more of a violet, then too much iodine is present 
and more water or zinc chloride should be added. 
Zinc chloride produces the blue color, iotline produces 
the red and the yellow colors and the addition of 
water serves to weaken the color that predominates. 

In some cases where it is necessary to examine all 
grades of paper, it is advisable to keep several stains 
on hand. A stain that gives the liest color on ground- 
wood and unbleached sulphite seldom gives a correct 
color on mixtures of rag, bleached sulphite and soda 
pulps. In such a case, make up one stain so that it 
will give a bright lemon yellow on a known sample 
of groundwood pulp and a slightly greenish blue on 
unbleached sulphite. For the mixture of rag, bleached 
sulphite and soda pulp, so adjust a second stain that 
the rag shows as a clear wine-red, the sulphite as a 
blue and the soda fibers as a dark blue. In testing 
out a stain always have on hand authentic samples 
of pulp so these mixtures may be made up. 

It is the hope of the paper testing committee that 
it will very soon have a set of standard mixtures, 
available for anyone desiring to make use of them 
in comparing with unknown samples. These stand- 
ards will also serve as a means of training the eye 
to judge proportion correctly. 

Note No. 4 — There are three kinds of cover glasses. The 
first two are very thin pieces of glass either round or square 
of approximately half an inch in diameter. The round or 
square cover glasses are necessary for high magnification 
and have one disad\ antage in that they are very fragile. 
The third type of cover glass is the same size as the micro- 
scope slide, and if thin microscope slides are used then a 
second microscope slide may be used as the cover for the 
first. The chief advantage of the large cover glass is that 
it permits three or four fields to be made up on each sildc. 

Note No. 5 — No definite recommendation is given in re- 
gard to the microscope magnification. This must be left to 
the individual preference. Satisfactory estimations may be 
made with a magnification as low as 45 diameters and 
equally satisfactory work is being done with magnifications 
as high as 120. The lower magnification has the advantage 
of giving larger fields, whereas the higher magnification 
gives more of the details of the markings of a fiber. The 
monocular and binocular microscopes both have their ad- 
vocates, and like the magnifying power, it is very largely a 
matter of getting used to a certain procedure. U'here only 
one microscope can be purchased it is better to use a mon- 
ocular, as it can be fitted with more attachments to suit 
special needs. It may be well to add that a low power of 
about 25 diameters for examining specks and surfaces, also 
a high power of 350 or 400 for details of fiber markings 
will often be found to be of use. Spence and Krauss in 



their article in Paf'cr, vol, xx, no. n, page 12 (May 23, 
1917), recommend a magnification of 160 diameters. 

The estimation of the fiber content is based on the 
relative proportion of the kinds of fibers contained 
therein, expressed on the percentage basis, consider- 
ing the total fiber content as 100 percent. In making 
a fiber estimation no account is taken of the percent 
of clay, alum, size, etc., that may be contained in the 
paper. It is always advisable to make up at least two 
separate samples of fiber taken from the test tube 
and the final result should be the means of all obser- 
vations on these two separate slides. In special cases 
it may be necessary to make up four separate fields. 

There are two methods of making the determina- 
tion for fiber content. One is the count method, the 
other is the estimation method. Both methods have 
their advocates and both give good results. This 
committee however, recommends the estimation 
method, believing it to have the following advant- 
ages : 

( I ) It is more accurate under certain conditions, 
namely, in making groundwood determinations, and 
<jf equal accuracy under all other conditions; (2) it 
it much quicker; (3) it is easier to teach an individ- 
ual to estimate correctly than to count correctly; 
(4) it is possible to make up standard mixtures for 
ready comparison. 

The estimation method involves training the eye 
In- the comparison of unknown samples with standard 
mixtures of known composition. The result of each 
observation on each part of a field examined, should 
be written down and the mean of all the observations 
is the result to be reported as final. Accuracy in the 
estimation method involves practice and continual ref- 
erence to known standards. Unstained slides of these 
standard mixtures should be kept handy to be made 
up in case there is any doubt about the sample being 
tested. 

There is a third method for fiber determination 
that has been proposed by Spence and Krauss 
(Paper, vol. XX, no. 11, page 11, May 23, 1917), 
which is worthy of description here and recommen- 
dation to the Technical Association. The procedure 
is as follows: Samples are made up as described un- 
der Note I, second method. The slide is placed un- 
der a microscope of 160 diameters and the lengths 
of the various fibers are ineasured in terms of the 
diameter of the field seen through the microscope. 
.\n adjustable stage is also essential as otherwise it 
w(.)uld not be possible to move systematically over the 
entire sample to be examined. After four samples 
have been estimated as above described, the figures 
are added together to get the total length of each 
kind of fiber present. The total length of each kind 
of fiber present multiplied each by its own weiglit 
factor gives a set of results that are directly coinpar- 
able and may be converted into the percent of each 
kind of fiber present. The weight factors as deter- 
mined by Spence and Krauss are as follows: Rag, 
1. 000; hemlock pulp, 0.870; poplar pulp, 0.454; birch 
[)ulp, 0.652; beech pulp, 0.525; maple, 0.365. This 
method, which is undoubtedly a step in the right di- 
rection, is recommended as a method to be used in 
cases of dispute between two different analysts. It is 
a very slow method and cannot therefore be used 
where manv- routine samples must be examined each 
day. The Spence-Krauss method is undoubtedly the 
only method that will enable a determination of the 
proportion of the various kinds of wood present, such 



P A P i; R T 1-: S T I N 



M i: r HODS 



as a mixture of hemlock, beech, poplar, birch, maple, 
etc. 

In any method of testing it is always advisable to 
make use of all possible apparatus that may be of 
assistance in carrying out the method described. 
There are no holders for microscope slides on the 
market, therefore a brief description will be givesi 
and it may be constructed at almost no expense for 
labor or material. 

The holder for the microscope slides is made ;is 
follows : take two pieces of brass }i inch thick by J.{> 
inch wide by 3 inches long (oak or maple may 1)C 
used if the brass is not obtainable), then cut a groove 
J-g inch wide by % inch deep along one of the longi- 
tudinal edges of the brass strip. This groove then 
serves as a rest for the glass slides. (See Plate i.l 
The pins (see sketch) serve to prevent the glass 
slide from slipping out of the grooves while the bun- 
dles of fibers are being tensed apart. Also note the 
parts on the sketch marked "Painted black" and 
"White surface." These serve as a background. The 
glass slide is placed over the black background when 
the unstained libers are first put on the glass slide, as 
the lighi (almost white) colored fibers show up best 
with a black background. After the Herzberg stain 
is added, the glass slide is pushed to the other end of 
the brass holder, which brings it over the white back- 
ground and causes the dark-stained fibers to show- 
up more distinctly and enables even the smallest liun- 
dles to be separated. 

STANDARD PAPERS FOR FIBER ANAEVSIS 

To check estimates of fiber analysis slides of fibers 
m known pro|)orti(>ns are niaile. Pure stock is beaten 
in a small beater and made into hand sheets. Sheets 
of the wariou-^ jjure fibers are kept under the same 
atmo-pheric cnnditioiis. T<i make u|i a field (if known 

CI--\SSIFIC.\T1()N OF VEGETAIiLE FIP.EKS I'SEIl IN PAPERlMAKINc. 

.\ — Seed Hair j Cotton 

I-^iber I Bomliax Wool — East Indies 

Flax or Linen 

Hemp — (Borders ol Mcdilcrrancan ) 
Jute or Calcutta Hemp 
B — Stem t Common Xctile 

Fiber ■, Nettle Fibers ] China Grass 

(Past family) | [ Ramie — Water-resisting 

i Sunn Hemp 
(Java 
Manila Hemp 
_ Straw and Esparto 

New Zealand Hemp 
Manila Hemp 

(2 Leaf Sisal or Dominuxi Hemp 

Filler ' ^''"^ Fillers (South America) 

Pineapple Leaf Filier 
Wool from Rreen 
Vegetable Wool from green 
( cones of Pine and Fir 



D— Fruit 

Filler 



Cocnainit Fiber 







Larcb-Tam;irack 






Fir 




Resinous or 


Spruce 




Coniferous 


Cedar 
Pine 


Fiber 

E— Wood 




Hemlock 
Cypress 
Birch 
Mulberrj- 




Nnn-resiiious 


Beech 




or Broad-leaf 


Gum 

Tulip Tree 
Poplar 



composition take weights of the pure fiber sheets and 
make up a total of at least 5 Gm. in proportions to 
;.;ive the percentage desired. Disintegrate and mix 
thoroughly by shaking with shot in a bottle or by 
the action of a small disintegrator. .Sample and make 
up the slide as for any disintegrated paper sample. 

STAINS F(1R SPECIAL PURPOSES 

There are many stains in use for special purposes 
mid a description of them is therefore advis.able. 

I'Jiloroijhtcinnl — Dissohe 5 grams of phlorogucinol 
in a mixture of 125 Cc. of distilled water and 125 Cc. 
Ill' concentrated livdrdchlnric aciil. The solution 




should lie kept in the dark as much as [xissible as 
it is prone to lose its staining property on exposure 
to light. This solution produces a magenta or wine- 
red color on groundwood pulp. The color ma}' easily 
be noted by aj)plying some of the stain tii a piece of 
newsprint paper. There is approximately So percent 
of groundwood in newspaper so that a deep magenta 
color is developetl. The depth of color is an indica- 
tion of the amount of groundwood present. A very 
light shade of color, however, does not necessarily 
prove the presence of groundwood, as partly cooked 
jute, partly cooked unbleached sulphite pulp, and 
srime other fibers are also slightly colored. 

Aniline Sulphate — Dissolve 5 grams of aniline sul- 
phate in 50 Cc. of distilled water and acidulate with 
one drop of concentratetl sulphuric acid. This stain 
produces a yellow color on papers containing a large 
percentage of groundwood. This stain is not quite 
as sensitive to groundwood as phlorogliiciiidl, luit it 
is easier to obtain and prepare. 

Para-nitroaniline — Saturated solution in concen- 
trated hydrochloric acid. This stain produces an 
orange yellow color in the presence of groundwood 
and other lignified fibers. 

The C. G. Bright Stain— This is used for distin- 
guishing between bleached and unbleached pulps. 



PAPER TESTING METHODS 



o 

o 
u 

o 



H 
O 
U 



(73 

H 
c/3 

Q 

l-H 

<1 

Oh 
Q 

< 



H 
H 



H 

:z: 
o 



c/5 

I— I [Jh 









b 






a 









wT 






























































^ 









^ 
























J 


^ 









•0 










*tn 




















1 


1 








£ 


i\ 


rt 


s 


s 


























o°- 












c 


s| 






E^ 


u 











w 


s 


" 






t « 


•5 i 






w ^ 


;z: 








5 


I^g 


OJ 


CJ 


^ 






c';^ 

W^ 


c^^ 






5j 


c/1 








■^ 


°< 


1 


E 


1 
[/J 
















-Td 


-^ 




















































'5 










D. 


2 


° e 












1 




















'T'C/'J 








J3 










-Q 














IeS 




^'S 






"S 


^. 






>• 










-O 


^^-n 


t- Cl. 




"^ 




^ 


2 


£ 


















ja JS t- 

Hut; 




■^^ 




wi. 


(5 









c— 


S C 

is 




e 
•5 












•^ ■* 


»^ 


S 








2^ 


E-= 


-5 £ 




-a 














° 


^13 








0*^ 








c 


l^; 


c 


3 


c 
Z 


3 

z 


"^•S 


^ 






-^ 




















~~ 
















































































u 


•2 ^ 








rt 














5 0. 


3 


13 


3 










a 
•0 

£^ 


2 


^ 

0^ 


1 


1 


1 
1 






^" 


;§ 


«;-3 


ot 


J c E 


^ 


z 


Z 


-^ 


>• 





OT 






J3 




i 


T? 




















,-^ 


% 






ra 
























1 


^M 




'-B 


^» 










^ 


?'c 


1 

33 




e 






'Z 


"o c 
"c"^ 







li 








c 

Is 




li 


"^ 


T3 


^ 






C " 


+-'"rt 


^ 


13 C 


" 








t^.S 


^ 


% bo 


jy 




'S 








«J3 


IS 
H 


dM 

wi 


fS t> 


ll 


z 


3 

z 


^5 


■5 


^ 4> 


ex 


55 


>! 












w 








« 
































u 
























J£ 








|x 
























S '^ 








E n 




\, 


1 




^_ 






3 3 

3 E 


? 


1 


5 










^ jg 


° M 


t M 


S. 


T3-0 
u *3 


1^ 
























■^S 














E 3 


u 


'-' 




£.° 


z 


z 


z 


6.£ 


°«. 


f^ 


z'-^ 


Z^ 




^. 
































° 


'i 


c 




^ 










'^■^ 


"■" 


> 










« 


3 


^ 
^ 




Is 


c 










tc 


5 





















1 








c "* 

3 C 


: 


o| 


■2 


-ri 


1 




Mt« 







■g 




C-M 


•J 


0) 


«J 


E'm'" 


2 


^^aj 


u 


" 


'^ 


























-t ^ 
















^ 


























^ 


u 


^ 


H 


K-S 


0:S 


z 


z 


z 


Q^-^ 


"" 


^fc 


^ 


:^. 


z 
















1 


1 




3 








1 


1 






1 


^ 


U 


c 




E 


1 

'S. 
w 




6 




P 


c5 


s 

£ 
'^ 





1' A I' !•: l; '1' IC S T I N G It E T H O D S 





-c 


•^ 




























o 




























° s 


o 
5 


i? 














-^x ^ 














■a 












































ijjl 












o ^ 


s: 


-a 
























c J5 


"^ <n 












c 




si 1 ^ 






„ 


*^ 


"o 


■5 1^ 


fS^ 


wow 


L 






_ 'l^'.. 


1 




<-Si=i 






5 r_ 


(J 


1 '^ 


E ^ 


























































































5 


'^ o 






.- J5 




















13 C 




3 c 






CT3 








«f| 








S 


S 


w 


Jl 


u v: 






■^ ov^ 




Y, 




a.Ho 







3 





u 


1 


'■i3 


-o 




c 


.a 












^ 


j: 








l*^^l 


^ 




jii 












'^ 


§ 


ci 


o 


o 




Ui M 


>1 




^ 


'a ^ 










^ 


Q 


t£ 


"■■t 


« 




l^i 


1:3 




S 


C 1, 










" 


" 


S J. 


1 ^ 


T 1 




[ ij'So ^ 


U rt 




u 


'5 E 










o 


£ 


I 3 


_C ^ 




































---- 


— -- 




--— 


£ i: 













----- 


— — 


£ S-. 




O ?, 
































































s 


^ 














> rt u 




^ 












^ t; 














>'.-^ rt 
















u J 














?ll 


^' 


c "■ 










c 




























































u « 


JS-a 














>> 


Q 


c 










-^ -J 




C 














=o 


vs 


1 




g 




SJ 




15 
























£^ 


^7^ 


u, 












CTu" 


- 


c < 


> 


04 1 > 1 















— 











— 





— 
















c 












-i 












iff 


o 




^ 




Tj ■" 


1 










5 






































1=1 


1 " 




■5 


E 




El 








f 


1 


1 




1 




*~ 




























a_ 


E 






^•a 




















^^ o 


" '■ 


.t: 




.E 










J3 












« t/) 


K S 


c 




C IJ c 








o o 




c i 


u 




































J n 


13 "^ 


-^ 


^ 


E 


'^ C c 








E 


"S,'^ 


^ o 


1 




£ 


1 C. Leaf 
! (From 


> 2 


"5 


15 5 




it! 
illl 








£";a ;:!; 




'<J 


'5 


J3 


1 


s 
















_u 














.o 




























































E 


^£'s 


:? ^ 




■J '5 








"si 






, 


t> 






n 




■§! 


1 


5*a 








-!"?= 
1^-^ 


^ 


v° 


I'i 


2 






§ 


,?r-2 




^ 


c xi 








c ? 3 


3 


f 1 


r " 


1^ s 


"§ 


"u 


c/l 








-5"^ r 




















a 1 


— H H 


>^- 


p 


H U .; 








J tc^ 


^ 


""^ 


^■""' 


p s. 


u 


C 














E 


=1 




S 






c"^ 


.S 


1 


1 

1 


■2 


a 


2 


E 




(2 


E 


o 


G 




•5 

(5 




^E 




! 1 




- 


r, 


"- 


' 


" 


o 


'- 


CO 


rr 


2 


: 


L' 


- i 



PAPER TESTING METHODS 



Solution A: Tenth normal ferric chloride solution 
equal to 2.7 grams FeCl36H.O per 100 Cc. distilled 
water. 

Solution B : Tenth normal potassium ferricyanide 
solution equal to 3.29 grams KJ^e (CN)^ per 100 
Cc. distilled water. 

Solutions A and B should each be fdteretl through 
a fresh filter into clear glass stoppered bottles. Equal 
volumes are mixed fresh whenever the reagent is 
used. 

Solution C: Substantive Red — O.4 gram of benzo- 
purpurin 4B extra (Bayer Co), o.i gram of examine 
brilliant red BX (Badische Co.) and 100 Cc. of dis- 
tilled water. Have water hot and stir in the dyes 
slowly. 

The staining solutions are used in tall narrow cyl- 
indrical beakers, which are set into a water bath. 
The slides are suspended in the beaker by a clamp 





PLATE 2A 

iine degree for a period not less than fifteen minutes. 
The dry slide is then dipped in distilled water to 
moisten it uniformly, so that air bubbles will not be 
formed when it is immersed in the stain. If air bub- 
bles are formed the fibers under the bubbles will not 
be stained. If dipping in water still leaves bubbles, 
Ihey can be removed by blowing across the slide from 
the edge. The slide is then suspended in the stain 
and left there for fifteen minutes at 35° Cent. It is 
then removed and washed, by dipping in and out of 
a beaker of distilled water six times and repeating; 




which holds them at their uj^per ends, the ckimjis 
resting across the top of the beakers. The bath is 
heated by a small bunsen burner with a pilot flame, 
so that when the re(|uired temperature is reachetl the 
pilot flame may be used to maintain the temperature 
at the required amount. A thermometer should he 
suspended in the stain and the beaker containing the 
stain should be as small as possible so as not to use 
too much stain at one time. 

In making up the slides for this staining method 
it will be necessary to use the dropper method as 
used by Bright and also by Spence. (See methods 
of making up microscoiie slides as outlined in first 
part of this report). This dro|)[.)er method involves 
dropping a dilute mixture of water and fibers upon 
the slide and then evaporating the water. The dry 
slide is then ready for staining. 

Method of using solutions A and B known as the 
potassium ferric ferricyanide stain. 

Mix equal volumes of solutions A and B, heat to 
35° Cent, in the water bath, regulating the pilot flame 
so that the temperature will remain constant within 




the process in a fresh beaker of water. The slide 
can then be placed wet into the red solution, but it 
is perli.aps better to dry it t)Ut so that the fibers will 
be stuck on tightly again in case they have been 
loosened to any extent b\' the treatment. 



T V. S T I NM ; 



M L T H D S 



Mellidil of using sniulinn (', the substnntivc red 
slain; A fresli snlulion is lieated in 45° Cent., and 
the slide, after moistcninf;- anil excludint^ liuMiles as 
before, is suspended in the sokitinn for li\e minutes 
at 45° Cent, and immediately washeil in two hcakers 
of distilled water. 

The slide is then dried and a cover glass placed on 
with a drop of balsam. 

Directions for assuring best results. 'J"o get the 
clearest, brightest results, distilled water must be used 
throughout, and the staining solutions must be fresh. 
The two solutions for making ferric ferricyanide will 
keep well if placed in sei)arale bottles. Equal vol- 
umes are mixed l(jgether immediately before using. 
The red solution should be freshly made each time 
for the best results, as it gets thick and stringy on 
standing, especially when it is being heated u[) con- 
tinually. 

.Staining under the conditions described gives an 
unbleached sulphite perhaps the deepest blue it is pos- 
sible to olitain without depositing blue on the slide 
and on the bleached sulphite; the method also pro- 
duces the best red on the bleached fibers without 
turning pur[)lc the unbleachetl fibers. Unbleached 
suli)hite from different mills varies considerably in 
lignin content, hence some samples stain a deeper 
blue than others. The foregoing conditions give a 
satisfactory blue on a sample of high grade imported 
unbleached pulp as well as a better color on the aver- 
age run of unbleached pulps, the latter being not so 
well cooked as a rule. With pul[) containing more 
lignin it is possilile to use a slightly stronger treat- 
ment with the red and thus get a better color on the 
bleached without aflecting the unbleached. 

After a man has had a little e.xperiencc with the 
methotl he can tell by the color of the unbleached 
fiber whether he may safely continue the staining 
with the red for six or possibly seven minutes at 45° 
Cent. At first, however, it is better to follow the 
directions as given. It is of prime im[>ortance to 
wash out or neutralize every trace of alkali in the 
libers, as the blue is decolorized by alkali. 

This method of sl.iining will in general give a dis- 
tinction between [jure cellulose fibers and those which 
contain lignin. Rags, bleached sulphite, soda pulp 
or any thoroughlv bleached material are stained red 
while unl)leached sulphite, groundwood, jute, or any 
lignified materials are stained blue. The princii)al 
ai)pIication lies in the estimation of unbleached pulp 
in book papers. A considerable saving can be made 
bv using unbleached sulphite instead of bleached, 
hence it is important to know how much unbleached 
pulp there is in a sheet. 

PHYSICAL TEST 

Area of sample — For convenience use a straight 
edge graduated into inches and tenths .'ind read to 
hundredths of an inch. Calculate area in s(]u:ire 
inches. 

U'eialit nf a sample — The sheet-weighing device 
that inilicates the equivalent weight in pounds in 
terms of a 500 sheet re.'im, is most suitable for lab- 
oratory or mill use. The quadrant type scale, sold 
l)y Cornelius Kahlen, New York City, is most easily 
handled as no sliding poise is required. (See Plate 
2.) In weighing very small samples, it is not desir- 
able to use a weighing device graduated in terms of 
a 500-sheet ream. For such cases a chemical bal- 
ance should be used and the weight in grams multi- 



plied b\- 1. 102, will give the equivalent weight of 
5<M) sheets of the size weighed. 

TJtrROVED QUADRANT SCALE 

Recent improvements in the quadrant type scale 
are shown in Plate 2-A. This scale is made by the 
Pi. F. Perkins Company, of Holyoke, Mass., and is 
designed to give the weight of a ream quickly without 
excessive loss of time due to swing of the basket 
or vibr.ilion of the indicator. 

Plate 2-1! shows another type of sheet weighing 
scale made bv the Tlnving instrument Company, 
Philadelphia. 

The weight of the sample should also be converted 
to the standard size (25x40, 500). This size is equal 
to an area of 1,000 square inches and is recom- 
mended for universal use in reporting all laboratory 
tests. To secure greater understanding of the sample 
in question, the weight should also be calculated on 
the trade size for that particular kind of paper. 

Fcjrmula for small sample weighed on chemical 
balance : 

(\vt. in grams) XI102 . , , 

-. i^-T- — , -^-- r— j— ==WClgIU 25x40, 500. 

Area ot the sample 111 square inches 

(wt. in grams)X(il02 )X(ar ca of trade size dc sireci)_ 

Aria of the samples in square inches. 

weight on tra<lc size desired. 

I'^ormula for sample weight on sheet paper scales : 
(wt. in th)X (1,000) ^„,„.i.;ht 25x40, 500, 



:\vt. on trade ! 



Area of sheet in square inches. 

(wt. in ttj)X(Area of trade sizejjesir^d) 

Area of ."iheci in square inches 
desired. 

Thei-e is a second type of sheet weighing scale on 
the market (See Plate 3) of the pea and beam type. 
This type of scales is customarily used in the paper 
mill, and is made by the Fairbanks Company. 

TO DETERMINE THE SUBSTANCE NUMBER 

The weight of a ream folio size, i/'X.^2" — 500, 
can be staled .-is substance number. 

A method for determining substance number on 
small samples by the anal}tical balance is as follows: 
A n.il piece of thin metal cut exactly 2"X2-i/i6" is 
held iqion the sample and a sharp instrument run 
around the edge of the metal. The sample cut ex- 
actly 2'''X2-i./i6" vceighed on the analytical balance 
has a subst.ance number c(|ual to the weight of the 
cut sample in centigrams. 

W'ri-jliMn etn'iqraii-s^-' SOT shcclsX .17-1 "H- '"■ Pcr ■^I'cel 

:: ^ : . — =sun- 

45,350 centisrams per pound X 4125 sq. m. m sam|ilc stance 

ninnher. 
Weight in ce nli-ram s X 187000 
187110 
BURSTING STRENGTH 

Tiiere arc two general l\pcs of apparatus used to 
determine bursting strength. One is of the hydraulic 
t\'pe in which the" paper' is clamped against a rubber 
(iiaphragm, through which the i)ressure is applied to 
a circular area of the paper measuruig one square 
inch. The Mullen tester (Sec Plate 4), made by 
n. F. Perkins & Sons, Inc., Holyoke, Mass., and the 
District of Columbia Paper tester (.Sec Plate 5), made 
by the District of Columbia Pa[>er Manufacturing 
Company of Washington, D. C, are of the hydraulic 
type. The second type of bursting strength apparatus 
is of the spring oper;ited metal plunger design m 
which the paper is clamped between annular ring.s, 



sulislanee nunihcr. 



PATER T E S T I N r, METHODS 



througli which a spring operated pkingcr is forced. 
The Ashcroft tester (See Plate 6) made by the Ash- 
~ro'ft Company, of New York, is the only one o) 
this type now on the market. 

The bursting strength to be of greatest use must 
be expressed in terms of the weight of the sample. 
This ratio of strength to weight may then be directly 



by the use of a spring micrometer having a hand thai 
travels around a circular dial. This dial is graduateii 
into thousandths of an inch. This direct reading type 
(See Plate 7) of thickness g-'ui^c should not be read 
closer than half of a thousandth, as they are not accu- 
rate beyond that point. The following is a list of 
manufacturers of this t\pe of thickness gauge : B. C. 




PLATE 4 

compared with the strength ratio of any other paper 
if the same standard size sheet is used in each case. 
The strength ratio is expressed as a percentage. 

Bursting strcngthXiOO 

Strength Ratio=: — ■ .- 

weight in pounds (on a size 25x40,500) 

THICKNESS TESTER 



PLATE 5 



. Anies Co., Waltham, Mass.; P.. F. Perkins & Son, 

The thickness of a paper may best be determined Inc., Holyoke, Mass.; Storrs & Bement Co., 140-150 



P A r i: R TESTING If E T H O D S 



Federal Street, Boston, Mass.; The Ashcroft Mfg. 
Co., 85-89 Liberty Street, New York; Cornelius 
Kahlen, 349 Broadway, New York. 

It is advisable to have all thickness gauges cali- 
brated before use.. This may best be done by secur- 
ing a set of standard sheet metal leaf gauges, which 




range from 0.001 to 0.015 inclies. This range of leaf 
gauges covers the ordinary range needed in testing 
most papers, and should be used periodically to sec 
that tlie instrument for measuring thickness remains 
accurate. 

For the purpose of obtaining a quick comparison 
of the relative compactness of several papers, the 
following formula is suggested : 
Thickness in thousandts of an inch 

-Xio,ooo=ReIativc com- 




(Wciglit 25x40, 5,00) 




PLATE 7 



M 



PAPER TESTING J[ E T H O D S 



The factor 10,000 serves to give a resultant figure 
more readily remembered. A very highly compressed 
paper may show a relative compactness=o.6oo, while 
a very spongy or fluffy sheet may hulk to 1.300. 
This last sheet is more than twice as hulky as th:: 
first sheet mentioned. 

BULK TESTERS 

The "bulk" of a paper is the thickness of a certairi 




PLATE 9 

number of i).igcs and applies more particularly to 
book papers where the printer desires a book of a 
certain number of pages to "bulk" one inch. Tlie 
"bulk" of a paper is measure<l by cutting out shoi I 
strips of paper, piling them up to the required num- 
ber and measuring the combined height of the pack. 
This measurement .may be made by the use of a 
Perkins bulk tester (See Plate 8), made bv B. !■". 



Perkins & Son, Inc., Holyoke, Mass. This instru- 
};icnt measures the bulk in inches, also the pressure 
nf clamping, and takes the place of the ordinary 
.graduated sliding clamp which is in common use. In 
specifying the bulk of a paper, where the hand clamp 
is used, it is necessary to specify whether heavy, me- 
dium or light pressure is used. In using the Perkins 
i)ulk tester, the pressure is specified in pounds per 
-.([uare inch, as indicated on the dial. 

MACHINE AND CROSS DIRECTIONS 

/\ disk of paper about 3 inches in diameter is 
■ 'ropped upon water. The valley formed by the curl- 
:i!g of the disk lies in the machine direction. 

Machine and cross directions may be distinguished 
by cutting two strips about 8 inches long and }i inch 
wide from the sample, the second one to be cut at 
r ght angles to the first. When these are put together 
.nd held upright by their lower ends one will bend 
iower than the other when tipped one way. By tip- 
[ling back in the opposite direction the stiffer strip 

'.'ill support the other. The strip bending least by 
'is own weight is cut in the machine direction. That 

■ending most is cut in the cross direction. 

FOLDING ENDURANCE 

The folding cnthuT.ncc of a paper is measured on 
a machine in which a strip of paper of definite width 
ar.d length is clamped. The clamps are held apart 
r.iidcr definite tension and the paper is caused to 
bend back and forth upon itself, until the fibers wear 
through at the line of folding. The number of 
double folds is recorded automatically. The Schop- 
[>cr folding machine, marketed by Cornelius Kahlen, 
New York (See Plate 9), is the only device so far 
made to carry out this test. A. B. Green, of Erie, 
I'a., has recently patented a new folding device. 
The folding strength of paper is dependent not 




I'LATK 9- A 



T 1-; STING J[ E T U O I) 



15 



only upon the strength and durability of the pr.per, 
but also is very largely iniluenced by the relative hu- 
midity. To perform this test in the most accurate 
manner it is therefore necessary to keep the relative 
humidity constant for all tests. This can only be 
done by the use of a room where the humidity is 
under control. Where sucli a room is not .■;vailab!e 
then note must be made of the percent rel;;l:ve hu- 
midity of the air at the time of the test. No tests 
should be attempted when the humidity is eitlier very 
high or very low. A relative humidity between 65 
and 70 percent is more easily attained throughout t!ic 
)ear and is the standard humidify recommended 1.; 
the paper testing committee. 

The folding factor is determined \>y the following 
formula : 

Folding endurance 
=Foldin!; factor. 



(weight 25x40, 500) 

The folding factor will vary between about o.i a;; 
200. 

TO CAUBRATE THE SCHOPPER FOLniNG MACHINE 

A machine along the lines of the one illustrated 
(Plate 9A) was designed at the Bureau of Standards 
for the purpose of calibrating the springs acting on 
the clamping jaws. This consists primarily of a 
stand on one end of which the tester can be screwed 
firmly. On the other end is provided a support, with 
leveling screws, on which may be mounted a wheel 
provided with knife-edge bearings. Around the rini 
of the wheel is a groove of about J/4" deep. This 
wheel should be made of three PI3S of wood, glued 
to prevent warping, and should be so balaticed that 
when mounted on the supports with the back of the 
ktiife edge horizontal, it will remain in any position 
within 45° either side of this without tending to ro- 
tate. The talile on which the folding tester is 
iitounted should be made large enough so that the 
machine can be set up with either jaw facing the 
large grooved pulley. The relation between the height 
of this table an<l that of the bearings for the knife 
edge supi)orling the grooved pulley should be such 
that a fine piece of thread resting on tlie base of the 
groove in the pulley and attached to the center of 
one of the clamping jaws, the other clamp being re- 
moveil entirely, will form a horizontal line. Aflcr 
the jaws have been properly marked for maxinntni 
extension according to Reid, Veitch and Sammet, 
one of the jaws with its spring holder and stand 
should be removed entirely from the machine a.nd 
the latter should then be mounted with the end with- 
out the jaw and spring toward the grooved pulley. 
A thread or very fine wire should be attached to t!ie 
center of the clamping jaw, passed through the re- 
ciprocating slot, the latter being locked in its neutral 
position, over the wheel, and tied to a i Kg. v/eight 
so that the latter swings free, and the thread falls 
entirely in the plane of the groove in the pulley. It 
the reciprocating part be locked in its neutral posi- 
tion and the ailgnment of the machine and pulL-y be 
carefully done, it v>'i!l be unnecessary to remove that 
part of the machine which carries the four shk'H 
rollers and through which tiie reciprocating pr-i'l 
passes. After setting up, care should be taken that 
the thread holding the weight does not touch aiiv 
part of the folding tester and that the sfjuare slniik 
of the jaw is entirely free from any contact with tlie 
sides of the square opening into which it fits. If the 
spring tension is correct the jaw will be drawn out 



by the action of the i kg. weight so that the mark 
previously made to square shank will be just visible. 
If this is not the case the spring tension should be 
adjusted by loosening the small set screw holding the 
knurled collar on the end opposite the jaw, after 
which the tension is adjusted by revolving this knurl- 
ed collar. The other jaw should be adjusted in the 
same way after reversing the machine, removing the 
jaw just calibrated and replacing the other. 

Note — In connection with the fo'dinp; fester attention 
shnuld be ralKd to tlie f.ict that it is nh^okifclv cs'icntial 




PLATE 10 

;1kU small steel wheels supporting the clatnping jaws be per- 
I'tctly round, well oiled and revolve easily, as the jaws 
move liack and forth. In one case the fact that one of these 
did not revolve caused an error of 25 percent in the results. 

TENSILE STRENGTH 

The tensile strength of paper is determined by the 
load, in pounds, required to break a strip of paper. 
The tensile strength machine, best known in the 
l>aper industry is the .Schopper tensile machine, mar- 
keted by Cornelius Kahlen, New York (See Plate 10). 
In this device (See Plate 10) a strip of paper 15 
Mm. (approxixmatcly 19/32 inch) wide by 180 Mm. 
long (approximately 7-3/16 inches) is clamped at 
each end and the clamps are moved apart until the 
;trip is broken. A suitable device indicates the pull 
n kilograms (ai»[)roxiniately 2.2\b) required to break 
he strip. As the English units of measurements are 
■ised on all other tests, it is recommended that the 
j)ad in kilograms per 15 Mm. width strip, be con- 
verted into pounds per inch of width. See following 
formula : 

<373)X (Tensile strength in Kg. per 15 Mm. width) = 
Tensile strength in lb per one inch width. 

A tensile strength factor may be determined by the 
following formula: 



i6 



PAl'ER TESTING METHODS 



(Tcnsi'e strength in fb i>er i inch width) 



=Tcnsile strength 



(Weight 25x40, 500) 
factor. 

The usual factor for tensile strength is known as 
the breaking length. This is the length of a strip 
which, if suspencled at one end, would break of its 
own weight. The following formula may be used to 
(lelermine the breaking length of a sample: 



(Tensile strength per i inch widtli) X (13.889) 



(Weiglit of 
length in yards. 



hcct 25x40, 500) 

(Tensile strength per 15 Mm. widlh)X (13,889) 

(3/3Xweight 25X40, 500) 
length in yards. 

The breaking length factor 1 
maximum of about 11,000 }'ar(ls 
mately 2,000 yards. 



^ Breaking 



=Breaking 

ill lange from a 
down to approxi- 



ELONGATION AT RUPTURE 



The amount of elotigaiion at the instant of rupture 
of a sti'ip of paper under tens'oii is measured on the 




.Schopper tensile strength machine. The result is 
llgured as a percent of the total (>ri;;-inal length. 

ABSORPTION 

The absorption of a blotting paper is indicated by 
the height in ntillimeters to which, in a given time, 
a liquid will rise by capillary ;'.ction, when one end 
of a strip of paper held vertically, is immersed in 
water. The height in nilllimclcrs to wdiich the liquid 
(preferably water) will rise in ten minutes is taken 
as a measure of the rel:iti\e .'ilisorplion of the paper. 

OPACITY AND TRANSI.UCENC Y 

The opacity or transluccncy of a paper may be 
measincd b)' the "contrast ratio" method, as de- 
scribed in Bureau of .Standards Circular No. 63. 



( Copy may be secured by addressing Bureau of 
.Standards, Washington, D. C.) Briefly, the method 
involves a determination of the difference in photo- 
metric brightness, or contrast, between a black and 
white spot, when covered with the material to be 
tested. The instrument used is a Martens photo- 
meter in a specially constructed box. (See Circular 
No. 63.) 

The figure expressing the "contrast ratio varies be- 
tween zero and one. Values nearer zero indicate a 
more transparent paper, such as onion skin papers, 
tracing papers, etc., and larger values indicate greater 
opacity. The highest grades of tracing cloth will 
have a "contrast ratio" as low as 0.20, while a paper 
for envelopes, where opaqueness is essential, should 
have a "contrast ratio" of not less than 0.90 (See 
riate II of apparatus.) 

ESTIMATING TEARING STRENGTH BY THE THWING 
TEARING TESTER 

A photograph of the Thwing tearing tester is 
shown in I'late loC. From this photograph it can be 
seen that the test is carried out on a small sample 
of paper punched from a sheet by a special punch 
attached to the tester. The sample is slit part way 
and has six alined perforations following the slit to 
guide the tear. The sample is then pinned to two 
pins, one of which is attached to a movable weight 
on ;:n arm carrying a recording pen, and the other 
attached to a sliding record card holder, which is 
moved by a motor drive. The machine is set in mo- 
tion l)y electric contact, and as the record card-holder 
moves horizontally and tears the sheet along the 
alined perfoi'ations, the resistance of the sheet against 
tearing between the perforations swings the sus- 
pended weight and d'ps the attached pen, so that it 
makes a continuous record of peaks across the card; 
e icli peak being recorded as a definite force in grams 
required to tear the paper between two perforations. 
The average of the five different tears between the 
perforations is taken as the force required to tear 
this paper in grams. The weights governing the 
force applied can be varied by changing their posi- 
tion (jn the lever arm, or by substituting light and 
heavy weights, thereby adapting the machine to make 
uniform graphic records for a wide range of papers. 

DEGREE OF SIZING 

A simple qualitative lest to indicate the effective- 
ness of the sizing as a preventive of the absorption 
of ink, may be made by using the Ink Flotation Test 
described by C. Frank Sammet, Circular 107 of the 
Bureau of Chemistry (The Detection of Faulty Siz- 
ing in Paper) also published in Paper, vol. x, 9, pp. 
15-16, Feb. 12, 1913. This method involves the 
drawing of a strip of paper over the surface of an 
iron tannate ink and allowing it to drain and dry 
naturally. Upon examination of the surface with a 
low power microscope, a well sized paper will shov/ 
no indication of the fiber having absorbed the ink. 
Anv variation in the depth of color on the surface 
will indicate a lack of uniform sizing. This test 
may be still further developed by erasing the surface 
with an ink eraser (a spun glass eraser is most suit- 
able) and again dipping the sheet as before. A pa- 
per well sized throughout the sheet will show little 
or no additional absorption of ink at the erased spot. 
This test is only comparative but may be valuable 
to a mill in checking the dail}' progress. 



PAPER TESTING METHODS 



The ink used fur the nl)ove test is made as fol- 
lows : 

Tannic acid (dry) 23.4 grams 

Gallic acid (crystals) 7.7 grams 

Ferrous sulphate 30.0 grams 

Dilute hydruchloric acid (11. S. P.)..., 25.00 Cc. 

Phenol i.o grams 

Blue Dye (Bavarian Blue S. & J. \'n. 47S) . 2.2 grams 
Water to make up to 1,000 Cc, alKnv 10 sctlle, and 
decant from any sediment. 
Note — ^Any water-soluble aniline blue, as mcihylcnc blue, 
may be used in place of Bavarian blue. 

Keep the temperature of the ink constant. Use 
llic ink hnt once. 



MEASUREMENT OF GLOSS 

The percentage of gloss or glare on papers of any 
furnish or color can be determined very readily by 
means of the Ingersoll glarimeter. See Plate loA.. 
A sample of the paper to he tested should be cut 
with such dimensions as to allow it to cover the 
whole area included by the spring clasp which is 
located at the foot of the polariscope. When the 
sample is clamped properly in the field of light, the 
case should be closed, and all unnecessary light ex- 
cluded from the room. Then, by rotating the eye- 
piece somewhere between the scale readings of 75' 
and IT5°, a point can be found where the two fields 




SIZING EFFECT — ALTERNATIVE METHOD 

For comparative sizing effect, squares 2"x2" are 
cut from each sample. These are subjected for at 
least thirty minutes to the same atmospheric condi- 
tions. Each square is then dropped upon an ink 
bath and the time in seconds recorded from the mo- 
ment the sample touches the ink to the penetration 
of ink through the upper surface of the sheet. The 
average of an equal number of determinations, at 
least six, is used for comparative sizing effect in 
each sample. It is absolutely essential that compara- 
tive tests be made under identical atmospheric con- 
ditions and by the same operator, because moisture 
content influences the penetration of the paper and 
different people have different judgments as to when 
the ink is "through." 



as seen through the polariscope are of equal brilli- 
ancy. This is the desired reading and should be 
checked within half a degree at least three times 
before being taken as final. When this reading in 
degrees is located on the graph or table which ac- 
companies the instrument, the corresponding per- 
centage of glare can be obtained directly. 

When difficulty is encountered in matcliing the 
fields while testing various colored papers, a light 
red stained glass should be interposed between the 
eye of the observer and the eyepiece. This elimin- 
ates all color differences and allows the light inten- 
sities to be matched very readily. 

Note — The IiiRcrsoU glarimi Icr was devised by Dr. L. 
R. Ingersoll of the Forest Products Laboratory. Uni\eisiiy 
of Wisconsin. The original article appeared in the Elec- 
trical World for March 21, 1914. 



PAPER TESTING METHODS 



RETENTION OF LOADING 

By retention of loading is meant that percent of 
the entire amount of loading material added to the 
beater, that is retained in the finished product. 

Secure about a five-pound sample of the filler to 
be used, being careful to select a representative sam- 
ple. Break up all lumps, spread on a flat surface, 
divide into four parts, b^^ dividing the pile by two 
lines at right angles to each other crossing at the 
center of the pile. Select two opposite quarters, 
mix and proceed as before. This is known as the 
"Quartering Method of Sampling." This quartering 
method is continued until about 25 grams of loading 
material is obtained, which is then placed in a bottle 
for further use. From this bottle, remove a i-gram 
sample, dry at 105" Cent, to constant weight and cal- 
culate percent of moisture in the loading material, 
l^lace the dried residue in a crucible and heat nt 
the full heat of a Meker burner until a constant 
weight is secured, then calculate the percent of water 
of composition in the dr\- clay. 

(Have clay in a finely divided state and stir fre- 
quently during burning.) 

Secure sample of pulps to be used and determine 
percent of moisture and percent of ash. Weigh 
pulp added to the beater. Weigh clay added to the 
lieater. After running the paper over the paper 
machine, secure several pieces as a representative 
sample, dry and make the ash determination on the 




PL.^TE lo-A 

above paper. The above mentioned data used in 
the following formulas will give the percent of clay 
useil and the percent retention. 

Let P =weight of pulp added (in poniids). 

C =wcight of clay added (in pounds). 

A =Percent ash in the finished paper. 

Ap^Percent ash in the pulp. 

Wc=Percent water of composition in the cl.iy. 

Mp=Pcrcent moisture in the pidp. 

Mc^Percent moisture in the clay. 

The formulae for percent of 
follows : 



should be 



(I) 7r of clay used 



looC 
~P~ 



(2) % retention = 

(3) Jr of clay nseil 
{.\) % retention 



100 AP 
C(ioo-A) 

100 C ( i-Mf ) 
PC l-MpT 
_ 100 PX(A-K) 



C(ioo-A-K) 

The value of Iv is the percent of filler not derived 
from the loading added. An average value of K is 



0.50 so lliat the formula (4) may be used as above 
or as follows: 

100 P(.'\-0.s) 

(S) % retention = 

C(ioo-A-O.s) 

Formulas (3) and (5) are recommended for use 
by the Technical Association of the Pulp and Paper 
Industry, though (i) and (2) may be used when 
accuracy is not essential or when the values for 
nioislurc content are unknown. Fomiula (4) does 





not take into consideration the percent water of 
composition in the loading. Where this known suit- 
able correction may be made. 

No account is taken of the ash from alum or 
rosin size as the maximum amount from these fac- 
tors is probably under 0.05 percent and therefore 
negligible. An ash determination need not be calcu- 
lated beyond the first place. (See ash determination 
under chemical testing.) 

SPECKS IN PAPER 

The appearance of a sheet may show imperfec- 
tions caused by foreign materials or malformation on 
the wire. These are the most common causes of 
poor-looking paper. 

Generally, specks need microscopic e.xamination. 
A Bausch and Lomb binocular microscope shown in 
Plate loB and a set of dissecting needles are use- 
ful. For chemical tests on small particles small test 
tubes made by sealing up one end of small glass 
tubing are convenient if the reaction is to be watched 
under the microscope. 

Rubber. This is very objectionable. It finds its 
way into the stock along with rag stock, sometimes 
as rubber paste in tire fabrics and the like, and 
sometimes in paper stock as rubber bands from office 
waste. 

Under the magnifying glass rubber sjiccks can be 
stretched by pinning down one end with a dissecting 



J9 



needle and pulling out the speck with another needle 
point. 

Rulil)er specks will give a characteristic rubher 
odor if burned by sticking into a flame on the end 
of a needle. They are soluble in cirbon tetrarli- 
loride. 

Rnsin specks. These are translucent ainbcr-col- 
ored specks so resembling rosin that they arc easily 
recognized. Proof of their identity can be had by 
dissolving the separated speck in ether in a small 
tube so that the action can be watched nnder the 
microscope. Qualitative rosin tests can lie ap[)lio;! 
to the speck as given under qualitative tests for 
rosin. 

Other specks resembling small bark particles may 
come from size which was made from im[)urc rosin 
without proper filtration. Althou';h not as translu- 
cent as the firdinary rosin sjieck (hey usu.illy earn 
enough rosin to respond to the qualitative test. 

Wood specks. Chips or wood fibers which might 
result from the accidental grinding off of a beater 
paddle or similar cause can be quickly iflentified iiy 
applying phloroglucinol ; they give a characteristic 
red coloration as in the groundwood test. 

Iron specks. Washer or beater bars, jordan.s, 
scaly pipes, corroded overhead ironwork, and iron 
buttons from rags contribute iron in metallic or 
oxidized form at times. The metallic particles will 
be attracted by a magnet after being freed from the 
sheet. The scale or oxidized iron can be dissolved 
in concentrated hydrochloric acid and a drop of 
potassium sulphocyanate added. Iron gives a char- 
acteristic wine-rerl color. This test can be applied 
to the separated particle in a small tube, or the 
sheet suspected to contain iron may be placed on a 
glass plate, wetted with concentrated hydrochloric 
acid for five minutes, and then with lo percent po- 
tassium sulphocyanate solution. Each iron speck 
shows red when the sheet is held up lo the light. 
The glass plate forms a convenient holder for the 
sheet. The red color fades in a few minutes and 
count should be taken immediately 

Another method is to immerse the piper in 2 
percent potassium ferroc\anide, then m j percent 
acetic acid, then wash well in water. Mang the 
sheets vertically until drw There will be a blue col- 
oration wherever there was an iron speck in the 
sheet. This method makes a more permanent recorrl 
than the sulphocyanate treatment. 

Oil spots. Oil spots are translucent and can he 
spread or thinned with ether or chloroform. Ex- 
traction with either of these solvents removes the 
oil, unless it is of a peculiar pasty formation caused 
by use of oily rags in the stock. Mineral oil in rags 
is prone to form a dirty congealed mass in the wash- 
ers, which specks the halfstuff with black specks in 
which mineral oil is the binder. Such specks in the 
finished sheet are not entirely removed by ether or 
chloroform. They are slightly translucent, and un- 
affected by solution in concentrated sulphuric acid. 

Color spots. Poorly ground colors such as poor 
ultramarine give a fine specky appearance usually 
identified by color only. 

Alum spots. These are usn.ally pulverized by the 
pressure of the calender rolls. They are soluble in 
water and give a slight acid reaction with indicators. 
This reaction is best watched by dissolving Ihe speck 
in a vei-y small test tube and adding the indicator 
while the tube is under the microscope and against 
a white background. 



Coal particles. Coal dust is insoluble and gives 
no color reactions with any reagent. In appearance 
iron scale can be mistaken for it, and in doubtful 
cases an iron test should be made on the sheet anil 
the unaffected lilack particles examined for coal. 

Under the microscope it can be seen that coal 
particles in a calendered sheet have been so pulver- 
ized b)' the pressure of the rolls that they shatter 
very easily when picked with a dissecting needle. 
Earge particles give a characteristic black smear 
when crushed and rubbed across the sheet. 

Btitton specks. Bone buttons ground by beaters 
or jordans into small pieces come through into the 
finislic<l sheet as a light colored powdered spot due 
to crushing in the calenders. A hole is often made 
at a button speck due to the crushed button piercing 
the sheet .-md then partly crumbling out after calen 
dering. Such specks can be differentiated from alum 
as the.\' are insoluble in water and give no acid re- 
action with the indicators. 

Paper specks. In slock ni.ide from old papers 
small undefibr'^l pieces may slide through the screens 
and form a speck on the sheet. Such specks are 
fibrous .-Hifl when lifted out of the sheet they can be 
defibred under the microscope with dissecting 
needles, sbuwiiig llieir identity by this characteristic. 

Foam spots Because of the depression left after 
each foam bubble there is a circular spot more tran,;- 
Iticont than the rest of the sheet formed wherever 
foam bursts on llie partly formed sheet. The restilt 
is characteristic, circular, and translucent as a small 
round watermark would look. 

Praij spots. Slock adhering to the .slices on the 
wire forms small uneven lumps when it drags off 
upon the sheet, 'fhese spots are not very common 
but can be recognized as an irregular formation hav- 
ing no foreign material present. 

Knots. Fabrics in rag stock with knotted threads 
very often show the knots in the finished sheet. The 
knotted thread is easily recognized under the mi- 
croscope. 

CHEMICAL ANALYSTS 

Ash determination — A one gram (Note No. 6) 
sample of the paper to be tested is burned in a por- 
celain or nickel crucible. A Mekcr burner is very 
convenient for this purpose, as some he.ivily loaded 
papers require considerable time and heat to burn the 
last traces of carbon. Ordinarily a white paper will 
give a white ash, but if mineral pigments have been 
used the ash is likely to be colored. In any case the 
.ish should be free -from specks of unburned carbon. 

Note No. 6 — The sample of paper need not be weighed 
closer than 0.C05 gram since a one percent variation in the 
moisture content will introduce an error of 0.01 gram. If 
the maximum error in the weight of the paper is o.oi gram 
then the maximum error in the weight of the ash will be 
o.oi gram for every 10 percent of ash present. Therefore 
in a paper containing 10 percent ash the results will be re- 
ported to the nearest tenths. If especial accuracy is re- 
quired the paper may be weighed in the "bone dry" condj- 
tion. Then with the error due to moisture eliminated it is 
possible to weigh the paper to +0.0005 gram and the error 
will be o.oooi gram for every 10 percent of ash. The results 
may then lie reported to the nearest hundredths. This lat- 
ter result will of course be i percent lower than the ash 
rcsnllc (jh a I gram sample containing 10 percent of mois- 
lurc. 

During the burning care must be taken that a por- 
tion of the ash is not lost by air currents. The ash is 
often light and fluffy, and the strong currents of air 
from the burners may blow away a portion of it. 
While cooling they may be kept in a dessicator, bu' 



PAPER TESTING METHODS 



this is not necessary, since the ash may be poured 
into a counterpoised aluminum (Note No. 7) pan as 
soon as the crucible is cool enough to avoid the dan- 
ger of loss from convection currents. The ash will 
cool almost instantly and may be weighed at once. 
This saves the time required for the crucible to cool 
and also avoids the necessity of weighing the crucible. 

Note No. 7 — Aluminum is recommended as being less 
easily broken as well as lighter, than glass. 

The ash as finally obtained includes all nonvolatile 
and noncombustible matter in the paper. It may be 
derived from at least five sources : 

I, The ash of the pulp from which the paper was 
made; 2, the ash from the various loading or filling 
materials added; 3, the ash from any surface coating 
or sizing, and 4, the ash of mineral coloring materials 
or pigments, and 5, the ash derived from alum size, 
though the amount traceable to this cause is very 
small and may be neglected. The complete quanti- 
tative analysis of an ash is a time consuming and also 
a rather complicated process. It is possible, however, 
to obtain some idea of the composition of the ash by 
a few comparatively simple tests. 

Once the paper is burned it is impossible to tell 
which portion of the ash is derived from the coating 
and which portion is derived from the tiller. There- 
fore, if anything more than the total ash content is 
desired the coating must be stripped from the paper 
before ashing. In the case of coated papers where 
casein has been used as the adhesive, this can often 
be done by the use of dilute ammonia. The insoluble 
material may be filtered ofif, dried and weighed. The 
filtrate may be evaporated to dr}'ness and the residue 
weighed. This will include the casein (or soluble 
casinates if such be present) as well as any soluble 
material present. The difference between the weight 
of the total ash and the ash of the paper 'from which 
the coating has been stripped plus the weight of the 
coating will give the weight of the combustible por- 
tion (i. e. glue or casein) of the coating. (Note No. 
8.) 

Note No. 8 — Provided the insoluble portion of the coating 
has been ignited to the same extent as the total ash. 

It is quite possible for a paper to have an ash of 
3 to 5 percent without being loaded. This might be 
due to the ash in the pulp, as well as to the ash de- 
rived from water, alum and sizing materials. 

Where the ash is 5 to 20 percent the paper is 
loaded. A list published in Paper for April 25, 191 7, 
gives the names of twenty-one loading materials. 
However, from the cliemical standpoint many of 
these are practically the same material sold under 
different names. They are all siHcates, sulphates or 
carbonates of aluminum, magnesium, barium or cal- 
cium. While an analysis will give the composition of 
the ash, it will not tell under what trade name the 
material may have been bought. 

KIND OF FILLER 

Burn enough paper to obtain at least 0.2 Gm. ash 
in a platinum or nickel crucible. Separate 1/3 of the 
ash from the main portion ; to this 1/3 add 5 Cc. 
water and boil until well extracted ; filter ; add a drop 
of hydrochloric acid to the filtrate and then 3 Cc. 10 
percent barium chloride solution. A white precipi- 
tate is due to calcium sulphate or crown filler in the 
paper. To the residue from the water extraction add 
dilute hydrochloric acid. Effervescence of carbon 
dioxide gas is due to chalk in the paper. This test 
for chalk may be applied directly to the paper before 



ignition if the presence of chalk is suspected at the 
start. 

To the 2/3 portion of the ash add i Gm. sodium 
carbonate and mix well. Fuse the mass in a plati- 
num crucible until it becomes a clear quiet liquid. 
Cool and dissolve in boiling dilute hydrochloric acid. 
This solution should be clear. If an undissolved 
white precipitate remains, filter this off. It is prob- 
ably due to barium. Dip a clean platinum wire in 
this residue and hold it in a bunsen flame. Barium 
will give a characteristic green color. This shows 
the presence of blanc fixe. 

If the previous hydrochloric acid solution was 
clear evaporate to near dryness. Dip a clean plati- 
num wire in this mass and test for barium as given 
above. Then take up the mass with dilute hydro- 
chloric acid; boil; filter. The residue is silica from 
silicates in the filter. A portion of this filtrate can 
be used as a confirmatory test for sulphates. To the 
filtrate from the silica separation add ammonium hy- 
droxide until slightly alkaline. A white flocculent 
precipitate shows the presence of aluminum. Filter 
off this precipitate and make the filtrate acid with 
oxalic acid. Make alkaline slowly with ammonium 
hydroxide. The formation of a white precipitate 
shows the presence of calcium. Filter off this pre- 
cipitate and make the filtrate alkaline with ammonium 
hydroxide. Add 5 Cc. saturated solution of sodium 
acid phosphate and stir with a rod. There will be a 
crystalline precipitate formed if magnesium is pres- 
ent. It forms slowly and is best brought down by an 
occasional rubbing of the sides of the beaker with a 
stirring rod. 

These tests indicate the possible combinations of 
elements in the filler. Where there are several names 
for one chemical combination — such as talc, asbestine, 
agalite, etc. — for various magnesium silicates a mic- 
roscopic analysis and comparison of the crystal form 
with known samples is necessary. Quantities of al- 
uminum invariably indicate clay. Silica and mag- 
nesium indicate talcs, agalites or asbestine and water- 
soluble sulphates from filler point to calcium sulphate. 

DETERMINATION OF PARAFFIN 

There are several paraffin solvents which may be 
used for this determination. Gasoline is easily ob- 
tained and comparatively cheap. It hns, however, the 
serious disadvantage of being very inflammable. Car- 
bon tetrachloride (CCl.,) is not combustible. It is 
superior to chloroform, since the fumes are not likely 
to produce anesthesia. Both gasoline and carbon 
tetrachloride have been found satisfactory. (Note 
No. 9.) 

NoiE No. 9 — Carbon tetrachloride cannot be kept in or- 
dinary "tin" cans on account of its action on iron. 

Enough of the paper must be taken to obtain a 
weighable amount of paraffin. One or two grams of 
paper should be sufficient. 

Place the paper in a Soxhlet or in an ordinary 
Erlenmeyer flask fitted with a reflux condenser, cover 
with gasolene or carbon tetrachloride and extract un- 
til the paraffin is all dissolved. If the Erlenmeyer 
flask be used it will probably be necessary to make a 
second extraction with a fresh amount of solvent. 

The solution may then be evaporated to dr3'ness 
and the paraffin weighed. If the paraffin shows a 
tendency to "creep" over the edge of the dish it may 
be easier to weigh the paper before and after extrac- 
tion and consider the loss in weight as paraffin. 



P A P F. R T F. S T I N 



i\r j: T H o D s 



QUALITATIVE TEST FOR ROSIN 

Boil a small porlion of the paper in 5 Co. acetic 
anhydride in a dry test tube. Cool. vVdd carefully 
down the side of the test tube a small amount of con- 
centrated sulphuric acid. The development of a p'.nk 
ring sliows the presence of rosin. 

Quantitath'e Rosin Dcteniiinatirn — Sammet 
Method: Alcohol-ether Method. 

Cut five grams of paper into strips approximately 
one-half inch wide and fold them into numerous small 
crosswise folds. Place the folded strips in a Soxhlet 
extractor and fill with acidulated alcohol diluted to 
approximately 3 percent made by adding to 900 Cc. 
of 95 percent alcohol, 95 Cc. of distilled waier ;'nd 
5 Cc. of glacial acetic acid. Place the .Soxhlet fl- sk 
directly in the boiling water of a steam bath a;:d ex- 
tract by siphoning from six to twelve times, accord- 
ing to the nature of the paper. Wash the alcoholic 
extract of rosin, which may contain foreign material, 
into a beaker and evaporate to a few Cc. on a steam 
bath. Cool, take up in about 25 Cc. of ether, transfer 
to a 300 Cc. separatory funnel containing about 150 
Cc. of distilled water to which has been added a 
small quantity of sodium chloride to prevent emulsi- 
fication, shake thoroughly and allow to separate. 
Draw off the water into a second separatory tunnel 
and repeat the treatment with a fresh 25 Cc. portion 
of ether. Combine the ether extracts which contain 
the rosin ami any other ether-soluble material and 
w.ish twice or until the ether layer is perfectly cleai- 
and the line between the ether and the water is sharp 
and distinct, with 100 Cc. portions of distilled water 
to remove salts and foreign matter. Should glue 
which is extracted from the paper by alcohol inter- 
fere by emulsifying with the ether, it may be readily 
removed by adding a strong solution of sodium chlor- 
ide to the combined ether extracts, shaking thor- 
oughl}' and drawing it off, repeating if nercssary be- 
fore washing with distilled water. Tiansifer the 
washed ether extract to a weighed [ilatinum dish, 
evaporate to diyness and dry in a water oven at 
from 98 to 100° Cent, for exactly one hour, cool and 
weigh. This length of time is sufficient to insure 
complete drying. Prolonged heating causes a contin- 
ual loss of rosin. 

Some objections have been made to portions of the 
foregoing method. It has been stated that the sodium 
chloride is sufficiently soluble in the ether to produce 
liigh results. .Some also prefer to cany the cvn.pora- 
tion of the alcohol extract to complete drMiess and 
then take up in ether and in writer. The residue as 
obtained is only partiall}- soluble in ether, Imt i!i c:;se 
the entire amount of ether-soluble material should not 
be secured, after as much has been di:-solved by the 
ether as possible, the remainder of the res'due is 
taken up in water. The ether and water is then sep- 
arated in a separatory funnel in the r.su'd manner. 
There appears to be no reason \vh\- a g'ass dish 
should not be as satisfactory as a platinum dish. Tt 
is also asserted that the extraction may be carried out 
in an Erlennie3-er flask instead of a .Soxhlet. Tne 
number of extractions required d?pcnd upon the 
character of the paper used. In some individual 
cases is has been found that a single extraction took 
out practically all the rosin. This extn;ction was 
done on a hot plate and the alcohol was in contact 
with the paper for about half an hoiu-. It is not 
known to what extent this time could be shortened or 
in what percent of cases a single extraction would be 
sufficiently accurate. 



Note — For extracting rosin, the apparatus shown in Plate 
I la will do the work of a Soxhlet extractor with greater 
convenience. It is essentially the same as the Soxhlet in 
principle, but can be set up very quickly, takes less solvent. 
Keeps the condensed solvent suriounded hy hot vapors, oc- 
cnpics less space, and is less liable to breakage. The time 
of extraction is lessened because of inore frequent flushing 
of the small well with the condensed solvent. This appara- 
tus is listed as an Underwriter's Extractor, and has bccu 
extensively used in the extraction of rubber. 

GLUE AND CASEIN 

There appears to be no cjuantitative method known 
for the determination of these materials in the pre.-^- 
ence of each other. Both substances contain nitro- 
gen. If only one be present and the nitrogen content 




of the original material as added to the jiaper be 
known, then by means of the nitrojcn iletermination 
the content of glue or casein may lie determined. 

QUALITATIVE TEST FOR GLUE 

Boil a small portion of the paper with 10 Cc. of 
water in a test tube. Decant the extract to anothe.' 
test tube and cool. Then add 5 Cc. of ammonium 
molybdate solution, followed by a few drops of nitric 
acid. The formation of a white amorphous precipi- 
tate shows presence of glue. 

DETERMINATION OF NITROGEN 

Place from three to five grams of the paper whicii 
has been cut into small pieces in a Kjeldahl digestion 
flask, add ten grams potassium sulphate, 0.7 gram of 
mercury and 25 Cc. of concentrated sulphuric acid. 

The nicrciuy acts as a catalytic agent aiding in the de- 
composition of the nitrogenous material. The potassium 
sulphate serves to raise the boiUng point of the sulphuric 
acid. It is probable that sodium sulphate can be used in 
place of potassium sulphate, but it is recommended that 15 
grams of sodium sulphate crystals be used in this case. 

Heat gently at first to prevent frothing and finally 
increase the heat as the digestion proceeds. At the 
finish the solution should be colorless, or of a pale 
straw color, and of a syrupy consistence. At the 
completion of the digestion, which may require one 
and a half to two hours, the contents of the flask are 
allowed to cool and 30 Cc. of a 4 percent solution of 
potassium sulphide are added. 

The potassium sulphide is ncccssaiy to break up nitrogen 
compounds of mercury. Ollii r innlerials than potassium sul- 
phide have been used for this purpose, but are not recom- 
mended. 



PAPER TESTING METHODS 



Before the distillation can be made the mass must 
be rendered alkaline. First dilute with about 200 Cc. 
of distilled water and then neutralize by adding an 
excess of a saturated solution of sodium hydroxide. 

The volume of the solution after the sodium hydroxide 
has been added should be aViout 400 Cc, therefore the vol- 
ume of water added must be calculated so that just enough 
room would be left for the sodium hydroxide solution. 
Commercial sodium hydroxide (95 percent) has been found 
satisfactory. 

There should be an excess of caustic soda equal to 
about 5 Cc. of a saturated solution. It is convenient 
to add a few drops of methyl orange indicator or 
phenolphthalein indicator solution to the flask before 
adding the sodium hydroxide. The solution will be- 
come yellow or red respectively when it becomes 
alkaline. 

The sodium hydroxide solution is carefully poured 
down the side of the flask so that it does not mix 
with the contents. The flask is immediately con- 
nected to the condenser and then the flask is shaken 
in order to thoroughly mix the contents. 

If about 5 grams of granulated zinc or a few small 
pieces of pumice stone are added to this flask just 
before the sodium hydroxide, they will help to pre- 
vent bumping. 

The distillate is caught in a flask containing a 
known amount of standard acid diluted to a volume 
of 100 Cc. with distilled water. (The equivalent of 
30 Cc. tenth normal acid should be ample.) A few 
drops of indicator should be added to this solution. 
Sodium alizarin sulphonate and methyl red have been 
recommended as indicators. The end of the con- 
denser tube should dip beneath the surface of the 
acid. The distillation should continue for forty-five 
minutes and the distillate should equal 200 Cc. Ti- 
trate with tenth normal alkali. 

This same operation of distillation should be car- 
ried out, using only the chemicals involved in order 
to have a check on their purity. This is known as 
the "blank." 

Subtract the number of Cc. of tenth normal alkali 
required to neutralize the distillate, from the number 
of Cc. required by the blank. This difference is the 
number Cc. of tenth normal alkali equivalent to am- 
monia. 

No. Cc.Xo.oi4=Gni. nitrogen. 

The following factors should be used on unknown 
samples: For casein use the factor 6.3 and for glue 
use the factor 5.6. In all cases this factor should be 
determined wherever possible, as those values will 
vary, depending on the grade of material used. 

NITROGEN DETERMINATION 

Note — Copper sulphate, wei!,'ht for weight, can be substi- 
tuted for the mercury as a catalytic agent in this determi- 
nation; it serves as an indicator for alkalinity by turning 
a characteristic blue when the solution is made alkaline pre- 
vious to distillation. Small glass beads can be effectively 
■iubstituted for granulated zinc to prevent bumping in the 
distilling flask. 

Starch Deterimnation — Qualitative test to indicate 
its presence in paper. 

Make a dilute solution of iodine in potassiurn 
iodide by adding a small amount of water to a mix- 
lure of three or four crystals of iodine and one gram 
of potassium iodide, stirring until the iodine is com- 
pletely dissolved, and then diluting the solution with 
pure water until a pale straw-yellow color is obtained. 
Add a drop of this solution to the paper under ex- 
amination, a l)lue color indicates the probable pres- 
ence of starch. If this blue coloration is obtained it 



is well to confirm the test by boiling the paper with 
water and testing the water extract with the iodine 
solution, because cellulose in the presence of water 
when subjected to certain mechanical processes gives 
rise to modifications known as hydrocelluloses. These 
hydrocelluloses are not soluble to any great extent in 
boiling water, but they will give rise to a blue colora- 
tion when brought into direct contact with the iodine 
solution. 

QUANTITATIVE ANALYSIS FOR STARCH 

Method of Kamm and Voorhees as described in 
Paper for August 27, 1919. 

Preparation of Reagents — The usual Fehling's so- 
lution is employed. 

Sol. A — 69.3 Gm. of crystallized copper sulphate 
are dissolved in water and the solution diluted to 
1000 Cc. 

Sol. B — 346 Gm. of Rochelle salt and 120 Gm. of 
sodium hydroxide are dissolved in water and the 
solution also diluted to looo Cc. 

Solutions A and B are kept separate and equal 
volumes mixed when ready to be used. In a given 
experiment, where it is reported that 10 Cc. of Fehl- 
ing's solution is used, it is understood that 5 Cc. of 
solution A is added to 5 Cc. of solution B. Accord- 
ing to the literature, 10 Cc. of such a .solution should 
be equivalent to 0.05 grams of dextrose when an 
analysis is run in a specified empirical manner. It is 
found more convenient to standardize the solution 
with a known quantity of starch, the latter being 
hydrolyzed and titrated under the same conditions 
used later for the hydrolysis and titration of starch 
in paper. The advantage is obvious. 

Potassium ferrocyanide solution. A 10 percent so- 
lution of K4FefCN)„3H,0 is used. 

Acetic acid solution. A 50 percent solution of 
acetic acid is found convenient. 

PROCEDURE FOR ANALYSIS 

The paper to be analyzed is tested with the usual 
iodine reagent. If but a trace of starch is present, no 
acetic acid is required in extraction. A 5-gram sample 
is cut into small pieces and placed in a 500-Cc. 
round-bottom flask. Two hundred Cc. of water is 
added, and 5 Cc. glacial acetic acid is run in, making 
a 25,-4 percent solution. The flask is connected with 
a reflux condenser by means of a clean rubber stopper 
and the contents boiled vigorously for i]^ hours. 
The extract is decanted through a Biichner funnel 
equipped for suction filtration and the pulp washed 
with about 50 Cc. of hot water. To the filtrate is 
added 15 Cc. of HCl (37 percent) and boiling con- 
tinued for thirty minutes, the volume of the solution 
being permitted to decrease by evaporation to about 
200 Cc. The hot acid solution is neutralized by the 
addition of solid sodium carbonate until effervescence 
ceases and the volume is determined. This solution 
is titrated into a measured quantity of Fehling's solu- 
tion (2 to 10 Cc, according to the amount of starch 
present). After each addition of sugar solution the 
mixture is heated to the boiling-point and maintained 
at that temperature for one minute. The reaction 
mi.xture may be diluted if this is considered desir- 
able. The end-point is determined on a spot-plate 
witli a potassium ferrocyanide-acetic acid solution 
and is that point at which no immediate color is pro- 
duced on the plate; it may be determined to within 
!4 to I Cc. of the sugar solution, depending on the 
volume of solution employed. It was found that the 
potassium ferrocyanide became colored when allowed 



M li r H O D s 



23 



MARKED 



Weight (25x40, 500)= 

Weight ( )= 

Buisting strength 

Thiclniess= 

Ratio buisting strength to wt. (25 x 40, 500) 



FIBER 
COM- 
POSITION 



CHEMICAL 
TESTS 



PAFEa Test KECunD 



Rag 

Chemical pulp, bleached . 
Chtmical pulp, unbleached 
Coniferous fiber .... 
Broad-leaf fibtf .... 
Ground-wood pulp . . . 
Manila and jute .... 



Ash . . . 
Total resins 
Animal size 



lbs. 
lbs. 
points 
inch 



:.'a, rHYSICAL TESTS 



Absorption in 10 inirjutes (Elemm) . 

Double folds (Schopper) 

Tensile sirengch (strip !S Tnm x 90 ms. ) 
Tensile strength per inch of width 

Elongation nt riipture , 

Bresking length 



/^. 



y^'^'^i^ 



ASH 
Crucible No. 
Wt. of Ash 
Per Cent Ash 



ROSIN 
Flfis): & Cass. Wo. 
Glass Dish + R. 
" " Empty 

Weight 0? Rosin 
Per C9nt P\osin 



0n!t 



mm 
Humbur 

kg 
ibs. 





BURSTING 
STRENGTH 

(Poinls) 






THICKNESS 

Onch) 


NO. 


TE.^'SllE STRr:NC nt 


I>ER CENT ELONGATION 
AT RUPTURE 


FOLniNG ENnURANCE 


NO. 


K, >.: \ 


..de 




Machine 
Direction 


Cro-,; 
_DirecU0Q 


Machine 
Direction 


Cross 
Direction 


o'lrec'tion 


Cross 
Direction 


1 










1 
2 
3 
4 
5 














2 






















3 






















4 






















5 


































6 


Mean 












7 






















8 










Tinsilo slrcngtli in Ibs. pir 1" wi,ltli = {TL-U!iiI.' sln■nl,^l^ in kg per 15 ima,vvKltb)y (3.7 !), 

Brealiius length in \;irJs=(Ti-nsiK- Btroneth in lbs. per 1" wiiltlOX (13,Ss',l)~(\Vt. in lbs. i«:t2:. x W, sun) 


9 










10 










Wt., in lbs., of roam ol r.iX)sb.-tt,= (Wt. t.t 1 bbtct in Kr;ims)x(1.10:;). 
Wt. in grams per 6q. ui.-liT=(Wt. in lbs. per 20 X ID, f'')l')X(l.l"b). 
















1 
. t 


Wt. in grama per S(i. niet.T = (Wt. in lbs. o( any ream l.f 500 sli.-et!.)..: lU"G.l::)^ (.\re,. u( -beet in -.j. in ). 
Wt. ol any SCO-sheet rcam=(Wl.iu.st;im3 per mi. metcr)XlArca ot sheet in t.i. in.).,-(l loO.U). 










NO. 


ABSORPTION IN 10 MINITTES 
Klemm Method 


11— 6li3 


/^^^/" 






^^ct^ 












1 








2 








3 








4 








5 





























PAPER TESTING METHODS 



to remain a number of days with the acetic acid, and 
that sharper and more distinct end-points can be ob- 
tained if the acid is added separately to the spot- 
plate when the test is to be made. One drop of each 
solution is used for a test. 

METHOD OF CALCULATION OF RESULTS 

It has already been suggested that Fehling's solu- 
tion be standardized against one of the ordinary 
starches used in paper manufacture. Such a pro- 
cedure is justified by the close agreement, in the re- 
ducing values of com-starcli, Hercules gum, feculose 
and dextrin. 

Example — A sample of corn-starch was dried at 
105° Cent, for three hours. An 0.500-gram portion 
was then weighed out and hydrolyzed with about 190 
Cc. of a 4 percent HCl solution during a period of 
thirty minutes. After neutralization with solid so- 
dium carbonate, the final volume was adjusted to 200 
Cc, and the solution titrated against 10 Cc. of Fehl- 
ing's solution ; 20 Cc. of sugar solution were required 
and 10 Cc. of Fehling's solution are therefore equiv- 
alent to 20X0.50=0.050 gram starch. 

200 

In an analysis of a 5-gram sample of paper the 
volume of the final hydrolysis mixture was 217 Cc. 
Of the latter solution 39 Cc. were required for reac- 
tion with 10 Cc. of Fehling's solution. The percent 
of starch in the sample of paper is therefore : 
2l7XValue of Fehling's solution expressed in grams of starch 

39 Wt. of sample of paper 

X 100 =5.5 percent. 

Since, however, a 5-gram sample of paper is used, 
and since our Fehling's solution is equivalent to 0.05 
gram starch to 10 Cc. of solution, the calculation is 
simplified thus: 

217 

=S-5 percent starch. 

39 . , , 

Mention might be made of the polarnnetric method 
(if Dr. C. E. G. Porst and H. A. Crown. See Journal 
of Iiulustrial and Engineering Chemistry, vol. 5, No. 
4, April, 1913. 

ANALYSIS FOR DKXTRINS IN PRESENCE OF BEATER 
STARCH 

(Method of Kamm and Tendick.) 
The procedure adopted consists in the removal of 
the surface sizing by a 45-minute leaching of the 
sample of paper with water at a temperature of 60' 
Cent. For a 5-gram sample 200 Cc. of water is used. 
The extract is removed by suction filtration and tiic 
soluble carbohydrate material hydrolyzed and esti- 
mated according to the procedure already described 
in detail. See Method for Ouantitative Determina- 



tion of Starch. The starch reinaining in the paper 
may then be isolated by the dilute acetic acid extrac- 
tion iTiethod recommended in the article on Starch 
Determination. 

CHLORINE DETERMINATION 

The determination of free chlorine in paper is 
carried on in a manner similar to that used in test- 
ing half-stuff; namely, take a small mass of the stuff 
to be tested, from the beater, press it with the hand 
and test with a few drops of potassium iodide starch 
solution. If free chlorine is present the character- 
istic blue color will be developed. 

For the testing of finished paper the determination 
is best carried out as follows : Cut the paper into 
small pieces, moisten with distilled water, and test 
with starch iodide paper; this is best done on a glass 
plate. 

Instead of starch iodide paper one may mix a 
small piece of starch to a paste with cold water, and 
mix it with a solution of potassium iodide. 

FREE ACID DETERMINATION 

Weigh 10 grams of the paper to be tested, tear into 
small pieces, place in a porcelain casserole and cover 
with a small amount of distilled water. Heat gently 
for an hour over water-bath or electric hot plate. 
Pour off water and wash with small quantities of 
distilled water, adding same to water extract. Make 
up to 100 Cc. according to directions given on page 
103 of Cohn's Indicators and Test Papers. 

The solution is then poured into a 100 Cc. Nessler 
tube (long form). A similar tube is filled with 100 
Cc. of distilled water to which has been added two 
drops of the litmus solution. To the former is then 
added tenth normal standard solution of caustic 
soda until the color matches the sample. The acidity 
is then expressed in terms of SO3. 

CONCLUSIONS DRAWN FROM TESTS 

For the general information of those who may 
undertake the laboratory testing of paper, it is especi- 
ally pointed out, that the most complete series of 
tests, will not alone tell all the important properties 
of a paper. In order that correct conclusions may 
be drawn, it is necessary to know something of the 
use to which the paper is to be put. This knowledge 
may be obtained only by experience, and by close 
observation and continual testing of the materia! 
used. Conclusions should not be drawn without full 
information regarding both the tests results and the 
actual working conditions of the paper. 

Complete laboratory records should be kept of all 
tests and in such a manner as to be always available. 
The accompanying 5x8 inch record cards are offered 
as a suggestion, though individual requirements may 
necessitate certain alterations. (See Plate 12.) 



